I don't know how much overall time I spent playing any one game.
The game I played the most would have to be Ghost Recon Advanced warfighter. I must have played for at least 2 years, 20 hrs week.
So that's about
2000 hours

The most hours of straight play would be
Command and Conquer Red Alert when it first came out.
38 hours straight with no sleep and only a few bathroom breaks.

i have 1205 days played on 1 character in world of warcraft, and about 300 hours on Anno 2070
and other games range form 1-50 hours.
but WoW is my main consumer, at least 5-9 hours a day for the past 5 years